1 // SPDX-License-Identifier: MIT
3 * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
5 * Based on bo.c which bears the following copyright notice,
6 * but is dual licensed:
8 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
11 * Permission is hereby granted, free of charge, to any person obtaining a
12 * copy of this software and associated documentation files (the
13 * "Software"), to deal in the Software without restriction, including
14 * without limitation the rights to use, copy, modify, merge, publish,
15 * distribute, sub license, and/or sell copies of the Software, and to
16 * permit persons to whom the Software is furnished to do so, subject to
17 * the following conditions:
19 * The above copyright notice and this permission notice (including the
20 * next paragraph) shall be included in all copies or substantial portions
23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
26 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
27 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
28 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
29 * USE OR OTHER DEALINGS IN THE SOFTWARE.
31 **************************************************************************/
33 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
36 #include <linux/dma-resv.h>
37 #include <linux/export.h>
39 #include <linux/sched/mm.h>
40 #include <linux/mmu_notifier.h>
43 * DOC: Reservation Object Overview
45 * The reservation object provides a mechanism to manage shared and
46 * exclusive fences associated with a buffer. A reservation object
47 * can have attached one exclusive fence (normally associated with
48 * write operations) or N shared fences (read operations). The RCU
49 * mechanism is used to protect read access to fences from locked
52 * See struct dma_resv for more details.
55 DEFINE_WD_CLASS(reservation_ww_class);
56 EXPORT_SYMBOL(reservation_ww_class);
59 * dma_resv_list_alloc - allocate fence list
60 * @shared_max: number of fences we need space for
62 * Allocate a new dma_resv_list and make sure to correctly initialize
65 static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
67 struct dma_resv_list *list;
69 list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
73 list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
74 sizeof(*list->shared);
80 * dma_resv_list_free - free fence list
83 * Free a dma_resv_list and make sure to drop all references.
85 static void dma_resv_list_free(struct dma_resv_list *list)
92 for (i = 0; i < list->shared_count; ++i)
93 dma_fence_put(rcu_dereference_protected(list->shared[i], true));
99 * dma_resv_init - initialize a reservation object
100 * @obj: the reservation object
102 void dma_resv_init(struct dma_resv *obj)
104 ww_mutex_init(&obj->lock, &reservation_ww_class);
105 seqcount_ww_mutex_init(&obj->seq, &obj->lock);
107 RCU_INIT_POINTER(obj->fence, NULL);
108 RCU_INIT_POINTER(obj->fence_excl, NULL);
110 EXPORT_SYMBOL(dma_resv_init);
113 * dma_resv_fini - destroys a reservation object
114 * @obj: the reservation object
116 void dma_resv_fini(struct dma_resv *obj)
118 struct dma_resv_list *fobj;
119 struct dma_fence *excl;
122 * This object should be dead and all references must have
123 * been released to it, so no need to be protected with rcu.
125 excl = rcu_dereference_protected(obj->fence_excl, 1);
129 fobj = rcu_dereference_protected(obj->fence, 1);
130 dma_resv_list_free(fobj);
131 ww_mutex_destroy(&obj->lock);
133 EXPORT_SYMBOL(dma_resv_fini);
136 * dma_resv_reserve_shared - Reserve space to add shared fences to
138 * @obj: reservation object
139 * @num_fences: number of fences we want to add
141 * Should be called before dma_resv_add_shared_fence(). Must
142 * be called with @obj locked through dma_resv_lock().
144 * Note that the preallocated slots need to be re-reserved if @obj is unlocked
145 * at any time before calling dma_resv_add_shared_fence(). This is validated
146 * when CONFIG_DEBUG_MUTEXES is enabled.
149 * Zero for success, or -errno
151 int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
153 struct dma_resv_list *old, *new;
154 unsigned int i, j, k, max;
156 dma_resv_assert_held(obj);
158 old = dma_resv_shared_list(obj);
159 if (old && old->shared_max) {
160 if ((old->shared_count + num_fences) <= old->shared_max)
162 max = max(old->shared_count + num_fences, old->shared_max * 2);
164 max = max(4ul, roundup_pow_of_two(num_fences));
167 new = dma_resv_list_alloc(max);
172 * no need to bump fence refcounts, rcu_read access
173 * requires the use of kref_get_unless_zero, and the
174 * references from the old struct are carried over to
177 for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
178 struct dma_fence *fence;
180 fence = rcu_dereference_protected(old->shared[i],
182 if (dma_fence_is_signaled(fence))
183 RCU_INIT_POINTER(new->shared[--k], fence);
185 RCU_INIT_POINTER(new->shared[j++], fence);
187 new->shared_count = j;
190 * We are not changing the effective set of fences here so can
191 * merely update the pointer to the new array; both existing
192 * readers and new readers will see exactly the same set of
193 * active (unsignaled) shared fences. Individual fences and the
194 * old array are protected by RCU and so will not vanish under
195 * the gaze of the rcu_read_lock() readers.
197 rcu_assign_pointer(obj->fence, new);
202 /* Drop the references to the signaled fences */
203 for (i = k; i < max; ++i) {
204 struct dma_fence *fence;
206 fence = rcu_dereference_protected(new->shared[i],
208 dma_fence_put(fence);
214 EXPORT_SYMBOL(dma_resv_reserve_shared);
216 #ifdef CONFIG_DEBUG_MUTEXES
218 * dma_resv_reset_shared_max - reset shared fences for debugging
219 * @obj: the dma_resv object to reset
221 * Reset the number of pre-reserved shared slots to test that drivers do
222 * correct slot allocation using dma_resv_reserve_shared(). See also
223 * &dma_resv_list.shared_max.
225 void dma_resv_reset_shared_max(struct dma_resv *obj)
227 struct dma_resv_list *fences = dma_resv_shared_list(obj);
229 dma_resv_assert_held(obj);
231 /* Test shared fence slot reservation */
233 fences->shared_max = fences->shared_count;
235 EXPORT_SYMBOL(dma_resv_reset_shared_max);
239 * dma_resv_add_shared_fence - Add a fence to a shared slot
240 * @obj: the reservation object
241 * @fence: the shared fence to add
243 * Add a fence to a shared slot, @obj must be locked with dma_resv_lock(), and
244 * dma_resv_reserve_shared() has been called.
246 * See also &dma_resv.fence for a discussion of the semantics.
248 void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
250 struct dma_resv_list *fobj;
251 struct dma_fence *old;
252 unsigned int i, count;
254 dma_fence_get(fence);
256 dma_resv_assert_held(obj);
258 fobj = dma_resv_shared_list(obj);
259 count = fobj->shared_count;
261 write_seqcount_begin(&obj->seq);
263 for (i = 0; i < count; ++i) {
265 old = rcu_dereference_protected(fobj->shared[i],
267 if (old->context == fence->context ||
268 dma_fence_is_signaled(old))
272 BUG_ON(fobj->shared_count >= fobj->shared_max);
277 RCU_INIT_POINTER(fobj->shared[i], fence);
278 /* pointer update must be visible before we extend the shared_count */
279 smp_store_mb(fobj->shared_count, count);
281 write_seqcount_end(&obj->seq);
284 EXPORT_SYMBOL(dma_resv_add_shared_fence);
287 * dma_resv_add_excl_fence - Add an exclusive fence.
288 * @obj: the reservation object
289 * @fence: the exclusive fence to add
291 * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock().
292 * Note that this function replaces all fences attached to @obj, see also
293 * &dma_resv.fence_excl for a discussion of the semantics.
295 void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
297 struct dma_fence *old_fence = dma_resv_excl_fence(obj);
298 struct dma_resv_list *old;
301 dma_resv_assert_held(obj);
303 old = dma_resv_shared_list(obj);
305 i = old->shared_count;
308 dma_fence_get(fence);
310 write_seqcount_begin(&obj->seq);
311 /* write_seqcount_begin provides the necessary memory barrier */
312 RCU_INIT_POINTER(obj->fence_excl, fence);
314 old->shared_count = 0;
315 write_seqcount_end(&obj->seq);
317 /* inplace update, no shared fences */
319 dma_fence_put(rcu_dereference_protected(old->shared[i],
320 dma_resv_held(obj)));
322 dma_fence_put(old_fence);
324 EXPORT_SYMBOL(dma_resv_add_excl_fence);
327 * dma_resv_iter_restart_unlocked - restart the unlocked iterator
328 * @cursor: The dma_resv_iter object to restart
330 * Restart the unlocked iteration by initializing the cursor object.
332 static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor)
334 cursor->seq = read_seqcount_begin(&cursor->obj->seq);
336 if (cursor->all_fences)
337 cursor->fences = dma_resv_shared_list(cursor->obj);
339 cursor->fences = NULL;
340 cursor->is_restarted = true;
344 * dma_resv_iter_walk_unlocked - walk over fences in a dma_resv obj
345 * @cursor: cursor to record the current position
347 * Return all the fences in the dma_resv object which are not yet signaled.
348 * The returned fence has an extra local reference so will stay alive.
349 * If a concurrent modify is detected the whole iteration is started over again.
351 static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor)
353 struct dma_resv *obj = cursor->obj;
356 /* Drop the reference from the previous round */
357 dma_fence_put(cursor->fence);
359 if (cursor->index == -1) {
360 cursor->fence = dma_resv_excl_fence(obj);
365 } else if (!cursor->fences ||
366 cursor->index >= cursor->fences->shared_count) {
367 cursor->fence = NULL;
371 struct dma_resv_list *fences = cursor->fences;
372 unsigned int idx = cursor->index++;
374 cursor->fence = rcu_dereference(fences->shared[idx]);
376 cursor->fence = dma_fence_get_rcu(cursor->fence);
377 if (!cursor->fence || !dma_fence_is_signaled(cursor->fence))
383 * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj.
384 * @cursor: the cursor with the current position
386 * Returns the first fence from an unlocked dma_resv obj.
388 struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor)
392 dma_resv_iter_restart_unlocked(cursor);
393 dma_resv_iter_walk_unlocked(cursor);
394 } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
397 return cursor->fence;
399 EXPORT_SYMBOL(dma_resv_iter_first_unlocked);
402 * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj.
403 * @cursor: the cursor with the current position
405 * Returns the next fence from an unlocked dma_resv obj.
407 struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
412 cursor->is_restarted = false;
413 restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq);
416 dma_resv_iter_restart_unlocked(cursor);
417 dma_resv_iter_walk_unlocked(cursor);
419 } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
422 return cursor->fence;
424 EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
427 * dma_resv_copy_fences - Copy all fences from src to dst.
428 * @dst: the destination reservation object
429 * @src: the source reservation object
431 * Copy all fences from src to dst. dst-lock must be held.
433 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
435 struct dma_resv_iter cursor;
436 struct dma_resv_list *list;
437 struct dma_fence *f, *excl;
439 dma_resv_assert_held(dst);
444 dma_resv_iter_begin(&cursor, src, true);
445 dma_resv_for_each_fence_unlocked(&cursor, f) {
447 if (dma_resv_iter_is_restarted(&cursor)) {
448 dma_resv_list_free(list);
452 unsigned int cnt = cursor.fences->shared_count;
454 list = dma_resv_list_alloc(cnt);
456 dma_resv_iter_end(&cursor);
460 list->shared_count = 0;
469 if (dma_resv_iter_is_exclusive(&cursor))
472 RCU_INIT_POINTER(list->shared[list->shared_count++], f);
474 dma_resv_iter_end(&cursor);
476 write_seqcount_begin(&dst->seq);
477 excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
478 list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
479 write_seqcount_end(&dst->seq);
481 dma_resv_list_free(list);
486 EXPORT_SYMBOL(dma_resv_copy_fences);
489 * dma_resv_get_fences - Get an object's shared and exclusive
490 * fences without update side lock held
491 * @obj: the reservation object
492 * @fence_excl: the returned exclusive fence (or NULL)
493 * @shared_count: the number of shared fences returned
494 * @shared: the array of shared fence ptrs returned (array is krealloc'd to
495 * the required size, and must be freed by caller)
497 * Retrieve all fences from the reservation object. If the pointer for the
498 * exclusive fence is not specified the fence is put into the array of the
499 * shared fences as well. Returns either zero or -ENOMEM.
501 int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **fence_excl,
502 unsigned int *shared_count, struct dma_fence ***shared)
504 struct dma_resv_iter cursor;
505 struct dma_fence *fence;
513 dma_resv_iter_begin(&cursor, obj, true);
514 dma_resv_for_each_fence_unlocked(&cursor, fence) {
516 if (dma_resv_iter_is_restarted(&cursor)) {
519 while (*shared_count)
520 dma_fence_put((*shared)[--(*shared_count)]);
523 dma_fence_put(*fence_excl);
525 count = cursor.fences ? cursor.fences->shared_count : 0;
526 count += fence_excl ? 0 : 1;
528 /* Eventually re-allocate the array */
529 *shared = krealloc_array(*shared, count,
532 if (count && !*shared) {
533 dma_resv_iter_end(&cursor);
538 dma_fence_get(fence);
539 if (dma_resv_iter_is_exclusive(&cursor) && fence_excl)
542 (*shared)[(*shared_count)++] = fence;
544 dma_resv_iter_end(&cursor);
548 EXPORT_SYMBOL_GPL(dma_resv_get_fences);
551 * dma_resv_wait_timeout - Wait on reservation's objects
552 * shared and/or exclusive fences.
553 * @obj: the reservation object
554 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
555 * @intr: if true, do interruptible wait
556 * @timeout: timeout value in jiffies or zero to return immediately
558 * Callers are not required to hold specific locks, but maybe hold
559 * dma_resv_lock() already
561 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
562 * greater than zer on success.
564 long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr,
565 unsigned long timeout)
567 long ret = timeout ? timeout : 1;
568 struct dma_resv_iter cursor;
569 struct dma_fence *fence;
571 dma_resv_iter_begin(&cursor, obj, wait_all);
572 dma_resv_for_each_fence_unlocked(&cursor, fence) {
574 ret = dma_fence_wait_timeout(fence, intr, ret);
576 dma_resv_iter_end(&cursor);
580 dma_resv_iter_end(&cursor);
584 EXPORT_SYMBOL_GPL(dma_resv_wait_timeout);
588 * dma_resv_test_signaled - Test if a reservation object's fences have been
590 * @obj: the reservation object
591 * @test_all: if true, test all fences, otherwise only test the exclusive
594 * Callers are not required to hold specific locks, but maybe hold
595 * dma_resv_lock() already.
599 * True if all fences signaled, else false.
601 bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all)
603 struct dma_resv_iter cursor;
604 struct dma_fence *fence;
606 dma_resv_iter_begin(&cursor, obj, test_all);
607 dma_resv_for_each_fence_unlocked(&cursor, fence) {
608 dma_resv_iter_end(&cursor);
611 dma_resv_iter_end(&cursor);
614 EXPORT_SYMBOL_GPL(dma_resv_test_signaled);
616 #if IS_ENABLED(CONFIG_LOCKDEP)
617 static int __init dma_resv_lockdep(void)
619 struct mm_struct *mm = mm_alloc();
620 struct ww_acquire_ctx ctx;
622 struct address_space mapping;
629 address_space_init_once(&mapping);
632 ww_acquire_init(&ctx, &reservation_ww_class);
633 ret = dma_resv_lock(&obj, &ctx);
635 dma_resv_lock_slow(&obj, &ctx);
636 fs_reclaim_acquire(GFP_KERNEL);
637 /* for unmap_mapping_range on trylocked buffer objects in shrinkers */
638 i_mmap_lock_write(&mapping);
639 i_mmap_unlock_write(&mapping);
640 #ifdef CONFIG_MMU_NOTIFIER
641 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
642 __dma_fence_might_wait();
643 lock_map_release(&__mmu_notifier_invalidate_range_start_map);
645 __dma_fence_might_wait();
647 fs_reclaim_release(GFP_KERNEL);
648 ww_mutex_unlock(&obj.lock);
649 ww_acquire_fini(&ctx);
650 mmap_read_unlock(mm);
656 subsys_initcall(dma_resv_lockdep);